Titanium-base alloys



Patented May 13, 1952 TITANIUM-BASE ALLOYS Robert I. Jaffee, Horace R. Ogden, and Daniel J. Maykuth, Columbus, Ohio, assignors, by mesne assignments, to Remington Arms Company, Inc., Bridgeport, Conn" a corporation of Delaware Na Drawing. Application March 2, 1951,

Serial No. 213,688

Claims. 1

This invention relates to titanium base alloys, and particularly to ternary alloys of titanium and aluminum with antimony.

The use of titanium as a structural material is limited by its relatively low strength and high cost, and it becomes desirable to alloy titanium with such other metals as will increase the strength to acceptable levels and preferably at the same time effect some reduction in the total material cost. Aluminum is a metal well suited to the attainment of these objectives, being low in weight, relatively low cost, and having a material strengthening effect on titanium. However, the amount of aluminum alone that can be added to titanium is limited by its adverse effect on ductility. Binary alloys of titanium with more than about 5% of aluminum are too brittle for most structural uses; and such binary alloys containing less than about 5% of aluminum do not possess sufiicient strength to be of general utility. A further strengthening is highly desirable.

The present invention comprises the discovery that the addition to titanium-aluminum alloys of 0.5% to about 5% of antimony effects a marked improvement in the properties of titanium-aluminum alloys of a given aluminum content, say 3.5% to 5%. The alloys show a rare combination of extraordinary strength with adequate ductility.

The metal used as a base for the alloys of the present invention may contain the interstitial contaminants, carbon, oxygen and/or nitrogen, up to at least the total quantity to be found in good quality commercial titanium. Carbon, for example, has been found to be beneficial when present in amounts between 0.02% and 0.3%, the latter being about the maximum amount which is soluble in alpha titanium. An excess of carbon tends to form embrittling carbides. For a typical alloy, a carbon content of 0.1% to 0.2% is desirable, but the optimum amount varies with other factors. a potent hardener of titanium but tends to cause embrittlement. The effect of the three contaminants being additive at a given strength level, the quantity of each which can be tolerated depends to a considerable extent upon the quantity of the others. The limiting factor is usually ductility, and the requirement as to ductility varies with the intended use of the alloy. Further, increasing the amounts of the substitutional metallic alloying ingredients tends: to decrease the tolerance for the interstitial components, particularly embrittling nitrogen. An alloy of high purity titanium with 5% aluminum will tolerate as much as 0.25% nitrogen, but the addition of one or two percent of another metal materially reduces nitrogen tolerance.

The alloys of this invention may be prepared by melt-casting in an atmosphere of argon, rolling at a suitable temperature, say 980 C., and annealing under conditions which will effect recrystallization, but not substantial grain growth or re-solution of carbides. A typical but by no means universal annealing treatment comprises soaking at a temperature of about 850 C. for about 3 /2 hours. The rate of cooling after annealing is not material, since in these alloys the titanium is all in' the alpha phase except for minor amounts which may be combined as titanium carbide. The properties of selected alloys of titanium of requisite purity with aluminum and tin, as annealed for 3 /1; hours at 850 0., unless otherwise noted, are as follows:

Typical properties of an alloy of substantially pure titanium with 0.25% carbon and 5% aluminum, as annealed for 3 hours at 850 C., are as follows:

Proportional limit p. s. i 72,000 0.2% offset yield strength p. s. i 91,000 Ultimate strength p. s. i 104,000 Elongation in 1 inch per cent.- 17

The properties of selected alloys embodying Nitrogen is the present invention, as annealed for 3 hours at 850 C., are as follows:

Propor- Filon V. H. N, 0.2% Ofi- Ultimate A1 Sb 0 Surface set Yield Strength a e? Bend T 1 Specimen broke with little or no deviation from modulus line.

In the torgeoing tabulations "bend ductility is the radius, expressed as a multiple of specimen thickness, to which the specimen can be bent to an angle of 75 without fracture It will be seen that the addition of as little as 0.5% of antimony substantially increases the strength of the titanium-5% aluminum alloy, with only a minor eiiect on ductility. Increasing the antimony content of 2.5% has a relatively minor effect, and a further increase to 5% ad- 4 from 0.02% to 0.3% carbon, balance titanium.

2. An alloy consisting essentially of about 5% aluminum, from 0.5% to 5% antimony, from 0.02% to, 0.3% carbon, balance titanium.

3. An alloy consisting essentially of about 5% aluminum, from 0.5% to 5% antimony, from 0.1% to 0.25% carbon, balance titanium.

' a. An alloy consisting essentially of about 5% aluminum, 0.5% antimony, from 0.1% to 0.25%

10 carbon, balance titanium.

versely aiiects ductility without material change 5-. An alloy consisting essentially of about 5% aluminum, 0.5% antimony, 0.25% carbon, balance titanium.

ROBERT I. JAFFEE. HORACE R. OGDEN. DANIEL J. MAYKUTH.

No references cited. 

1. AN ALLOY CONSISTING ESSENTIALLY OF FROM 3.5% TO 5% ALUMINUM, FROM 0.5% TO 5% ANTIMONY, FROM 0.02% TO 0.3% CARBON, BALANCE TITANIUM. 